Law of Segregation

The law of segregation is Mendel's principle that the two alleles for a single trait separate (segregate) during gamete formation. This means each gamete receives only one allele of each gene, giving offspring an equal chance of inheriting either allele from a parent.

• In a heterozygous individual (Aa), half the gametes will carry A and half will carry a - this 50/50 split is due to segregation of alleles during meiosis.
• This law explains why recessive traits can reappear in the F2 generation: alleles that were paired in parents separate into different gametes and recombine in offspring.
• Law of Segregation deals with one gene at a time (one pair of alleles). It's different from independent assortment, which involves two or more different genes.

• If a genetics question asks why each gamete has only one copy of a gene, it's invoking the law of segregation. For example, a monohybrid cross yielding a 3:1 ratio in F2 supports this law.
• A classic Punnett square scenario (Aa x Aa) assumes allele segregation: each parent produces gametes with A or a in equal proportion. Recognize that this stems from the law of segregation.